Fuel and air injection quantities supplied to an engine are controlled to meet fuel economy requirements and emission standards. Closed loop control systems sense oxygen levels in exhaust flowing from the engine in order to control air and fuel quantities flowing into the engine. If engine components such as fuel injectors malfunction fuel and air injection quantities may not be accurate. Inaccuracies in injection quantities may increase emissions and/or decrease fuel economy.
If a fuel injector malfunctions, it is commonly due to contaminates in the fuel injector. Sediment within the fuel or fuel tank may contaminate a fuel injector. Contaminated fuel injectors can increase emissions, smoke, and/or engine noise. Conventional methods of diagnosing a contaminated fuel injector require removal of the fuel injector from the engine in order to test the fuel injector on a flow bench. Disassembly of an engine can be both time consuming and costly. Furthermore, an operator of the vehicle receives no indication of the malfunction until the vehicle has been brought to a service station.